The present invention relates to a method for metering or dosing a pharmaceutical product into capsules. The present invention also relates to a machine for performing the above method.
Metering or dosing of pharmaceutical products, generally as powders, into capsules is obtained using machines in which a metering unit fills the empty capsules with a pre-determined quantity of product. Thereafter a testing unit checks a sample of full capsules to determine statistically if the quantity of product within the capsules lies within an acceptable range. The measurement of the quantity of product metered into the capsules is generally an indirect type of measurement and is obtained by evaluating the difference between the weight of a full capsule, detected by the testing unit, and the average weight of capsules known from the type of capsules employed. This method involves the disadvantage of a somewhat imprecise determination of weight, in particular when the weight of the quantity of product to be metered into the capsules is of the same order of magnitude as the weight of the capsules themselves. In fact, the tolerances of the weight of product and of the capsule can compensate one another with the result that an evaluation of the weight of the product is obtained which is significantly less or greater than the real value.
In other types of machines, the uncertainty in the average weight of empty capsules is eliminated by using a method in which the testing unit weighs a full capsule and subsequently pierces each weighed capsule to evacuate the product from the capsule itself by suction. Finally, the emptied capsule is weighed and the difference between the weight of the capsule full and the weight of the capsule after having been emptied is evaluated. However, even this method involves the disadvantage of inexact weighing of the pharmaceutical product both because not all of the product is always emptied from the capsule and because the measured weight of the empty capsule is defective by the slivers of capsule removed upon piercing.